Conventionally, in order to display an image on a large screen by a liquid crystal display apparatus, a junction unit has been formed by joining a plurality of liquid crystal modules as a liquid crystal display element so that one image has been displayed by using the junction unit.
As to methods for joining such a junction unit, a method for joining a plurality of liquid crystal modules which is arranged such that a liquid crystal is injected between at least two substrates (Japanese Examined Patent Publication No. 62-8771/1987 (Tokukosho 62-8771)) as a first method, and a method which uses a plurality of substrates, which are joined to one another, on one side and which uses one substrate with a large area on an opposite side (Japanese Unexamined Patent Publication No. 1-213621/1989 (Tokukaihei 1-213621)) as a second method are suggested.
In the first method, as shown in FIG. 23, a front substrate 41 and a rear substrate 42 which have a rectangular plate-like shape are laminated by applying sealing resin 43 to all three sides of the substrates except for a side to be joined. As a result, an opening is formed on an end of the side to be joined. Here, in order to applying an electric field to liquid crystal 44, an electrode 41a is formed on the front substrate 41 and an electrode (not shown) on the rear substrate 42.
Successively, in the first method, the liquid crystal 44 is injected into gaps among the front substrate 41 and the rear substrate 42 and the sealing resin 43 from the opening, and the opening is temporarily sealed with an adhesive material 46, such as soft solder, epoxy resin, so that liquid crystal modules 45 are produced. Thereafter, the sealed end of each liquid crystal module 45 are deposited on each other so that the junction unit is formed.
Meanwhile, in the second method, as shown in FIG. 24, an adhesive 52 composed of polymeric materials is applied to ends of a pair of substrates 51, on which an electrode and a driving circuit for applying an electric field to liquid crystal are previously formed, and the ends of each substrate 51 are stuck by pressure so as to be joined by the adhesive 52.
A junction distance between ends of each substrate 51 which have been joined in such a manner is approximately 50 .mu.m, so it is set smaller than a size of one picture element of the liquid crystal display apparatus. On the junction end of each substrate 51 which has been joined in such a manner, the adhesive 52 is protruded from the surface of each substrate 51, so this causes irregularities of the gap between the substrates 51 and a counter substrate 53.
Therefore, in the second method, a laser beam 54 is irradiated to the protruded portion of the adhesive 52 so that the protruded portion of the adhesive 52 is removed, and the height of the protruded portion at a junction section between each substrate 51 is lowered to not more than 5 .mu.m. Thereafter, the counter substrate 53 and each substrate 51 are laminated so that a gap for injection of the liquid crystal 55 is formed, and the liquid crystal 55 is injected into the gap so that the liquid crystal display apparatus is produced.
However, in the conventional first method, immediately after the liquid crystal 44 is injected into the gaps, the opening of the gaps is temporarily sealed with the adhesive material 46 so than the liquid crystal modules 45 are produced. Then, the liquid crystal modules 45 are connected to each other, so it is difficult to control a sealing shape and a dimension of its junction section, namely, a shape of the adhesive material 46, thereby, arising a problem that secureness of sufficient sealing adhesive strength by the adhesive material 46 is difficult.
In addition, in the first method, in the case where a width of the junction section is set larger than a pitch of a picture element in order to secure the sufficient sealing adhesive strength, since the pitch of the picture element between the liquid crystal modules 45 changes greatly, images formed by each liquid crystal module 45 become something strange, so the images is difficult to see.
Therefore, in the first method, since the sealing shape of the junction section of the joined liquid crystal modules 45 directly influences quality of displaying, sealing pattern formation with high accuracy and high precision is required, thereby arising a problem that it is troublesome to produce a liquid crystal display apparatus having a large screen.
In addition, in the first method, in the case where epoxy resin is used as the adhesive material 46, a solvent included in the adhesive material 46 is dissolved out, and it may cause deterioration in characteristics of the liquid crystal 44. The deterioration in characteristics of the liquid crystal 44 adversely affects the quality of displaying, namely the quality of displaying is deteriorated.
Meanwhile, in the above-mentioned second method, in order to maintain high image quality, the height of the protruded portion at the junction section between the substrates 51 is lowered to not more than 5 .mu.m, but a special process, such as a laser process is required for removing the height of the protruded portion between the substrates 51. As a result, not only process of production is complicated but also costs of production becomes expensive.
In addition, in the second method, since the liquid crystal 55 is injected into the gap with a large area, not only a large-sized injection unit is required but also it takes much time and trouble to uniformly inject the liquid crystal 55 into the gap.